Study of PDK1 kinase conformations and potential regulatory mechanism for substrate activation (Póster))

MARIANA SACERDOTI; LISSY GROSS; ABHIJEET GHODE; ANDREW M. RILEY; SEBASTIÁN KLINKE; GANESH S. ANAND; KRISTINA PARIS; EVELYN SUESS; MARÍA V. CAPPELARI; PEDRO F. ARAMENDÍA; ALEJANDRO E. LEROUX; BARRY V. POTTER; CARLOS J. CAMACHO; RICARDO M. BIONDI

Evento online debido a la pandemia de coronavirus

Congreso; XLIX Reunión Anual de la Sociedad Argentina de Biofísica (SAB); 2021

Sociedad Argentina de Biofísica (SAB)

Phosphoinositide-dependent protein kinase 1 (PDK1) is a master kinase of the PI3-kinase signalling pathway that phosphorylates at least 23 other evolutionary related AGC kinases. It has an N-terminal kinase domain, a linker region and a C-terminal PH domain. Our laboratory has previously used a chemical and structural biology approach to study and characterize the bidirectional allosteric regulation between the PIF-pocket, a regulatory site located on the small lobe of the kinase domain, and the ATP-Binding site of PDK1. Phosphorylation by PDK1 is required for the activity of all substrates: they are phosphorylated either constitutively or with different timing upon PI3-kinase activation. Most substrates, like S6K, SGK, PKC, PRK/PKN, rely on a docking interaction where a C- terminal hydrophobic motif (HM) interacts with the PIF-pocket of PDK1. Interestingly, the interaction with the PIF-pocket of PDK1 is not a requirement for the phosphorylation of PKB/Akt after PI3-kinase activation, but both proteins have a PH domain that can bind PIP3 at the cell membrane and colocalize. However, we believe that other mechanisms must regulate that interaction since there are reports of PKB/Akt activation by PDK1 in the absence of PIP3. PDK1 has also been described to dimerize. We describe the effect of inositol poli-phosphorylated molecules and present results of a screening performed in order to find small compounds to regulate dimer formation. We conclude that PDK1 could exist as an equilibrium of dynamic conformations that may impact on the selective interactions with substrates. We suggest dimerization could also be part of the mechanism by which PDK1 phosphorylates some substrates like PKB/Akt. This potential new regulatory mechanism could be new approach to develop innovative drugs to target PDK1 and achieve, for example, PKB/Akt selective inhibition.